Electric motor brush apparatus and method

ABSTRACT

A motor assembly includes: a motor housing including: at least one brush receptacle having top and bottom ends; a locking element extending from the top end toward the bottom end; and a housing spring member; at least one brush holder apparatus including: a brush holder housing sized to be received within the brush receptacle, including: an upper surface and a lower surface; a receiving aperture; and an open end; a brush spring enclosed by the brush holder housing; and a brush located inside the brush holder housing; wherein the brush holder apparatus is inserted inside the brush receptacle; and wherein the housing spring member urges the brush holder apparatus toward the top end such that the locking element is received inside the receiving aperture.

I. BACKGROUND

This invention pertains to the art of installing motor brush holdersinside a motor. It is known in the art to secure a brush housingapparatus to an electric motor housing by using an interference fitbetween the outside surface of the brush housing and a receiving surfaceon the motor housing. The brush housing may be further secured byapplying adhesive to the assembled parts. This method of attachment maybe expensive as the interference fit requires exacting tolerances toboth mating parts. These tolerances can add cost to the assembly. Alsothe choice of adhesive may be difficult as the brush operates in a hightemperature and high vibration environment.

It is also known in the art to use straps and fasteners to secure thebrush to the motor housing. This method adds additional parts andadditional assembly time to the motor. Another known securing method isto add tabs to the outside of the brush apparatus and locate the brushin a receptacle formed in the motor housing. The brush is then securedin the housing by bending the tabs over the receptacle. Bending the tabsaccording to this method adds assembly time and thus cost.

One known method to electrically connect the brush apparatus to themotor field is to extend a conductive wire from the brush andelectrically connect the wire to a wire extending from the motor field.This method adds additional assemble steps and time to the electricmotor assembly.

What is needed is a durable, efficient, simplified, and cost-effectivemethod and apparatus to electrically connect and secure brushapparatuses and field windings of electric motors without usingadhesives, fasteners, or wire splices.

II. SUMMARY

In accordance with one aspect of the present invention, a motor assemblyincludes: a motor housing including: at least one brush receptacleextending along a longitudinal axis of the brush receptacle and having atop end and a bottom end that are substantially parallel to thelongitudinal axis; a locking element extending from the top end towardthe bottom end of each brush receptacle; and a cantilevered housingspring member having a distal end extending substantially along thelongitudinal axis and extending from the bottom end toward the top endof each brush receptacle; at least one brush holder apparatus including:a brush holder housing sized to be received within the at least onebrush receptacle, including: an upper surface and a lower surface thatare substantially parallel; a first receiving aperture in the uppersurface configured to receive the locking element when the brush holderhousing is inserted inside the at least one brush receptacle; and anopen end that is substantially perpendicular to the upper surface; abrush spring enclosed by the brush holder housing; and a brush locatedinside the brush holder housing but urged out of the open end of thebrush holder housing by the brush spring along the longitudinal axiswhen the brush holder housing is inserted inside the at least one brushreceptacle; wherein the at least one brush holder apparatus is insertedinside the at least one brush receptacle along the longitudinal axis;and wherein the housing spring member urges the at least one brushholder apparatus toward the top end of the at least one brush receptaclesuch that the locking element is received inside the first receivingaperture.

In accordance with another aspect of the present invention, a motorassembly includes: a field including: a laminated stator; at least oneterminal block secured to the laminated stator and including a connectorreceptacle; field windings; and at least one wire electrically connectedto the field windings and positioned partly in the connector receptacle;at least one conductive connector including: two substantially flat andparallel displacement members, each including: a top portion; and adistal portion including a cutting portion extending from the distalportion toward the top portion and configured to receive the wire; andtwo connector spring members, each including: a substantially flat lowerportion adjacent to, connected to, and substantially perpendicular to atleast one displacement member; and an upper portion extending above thetop portions of the displacement members and cantilevered alongsubstantially a connector axis of the connector; wherein the cuttingportions of the displacement members align along the connector axis, andwherein the displacement members are substantially perpendicular to theconnector axis; wherein the top portions of the displacement membersdefine a brush receiving plane; wherein the distal portions of thedisplacement members extend below the lower portions of the connectorspring members; and wherein the upper portions of the connector springmembers are angled toward each other at cantilevered ends, defining withthe brush receiving plane a brush receiving channel along the connectoraxis, wherein the brush receiving channel narrows in the direction ofthe connector axis toward the cantilevered ends; and at least one brushholder apparatus including: a brush holder housing sized to be receivedwithin the brush receiving channel, comprising an open end; a brushspring enclosed by the brush holder housing; and a brush located insidethe brush holder housing but urged out of the open end of the brushholder housing by the brush spring along the connector axis when thebrush holder housing is inserted inside the brush receiving channel;wherein the at least one connector is inserted into the connectorreceptacle such that the cutting portions of the displacement membersreceive and make electrical connection with the at least one wire; andwherein the at least one brush holder apparatus is inserted inside thebrush receiving channel of the at least one connector along theconnector axis in the direction of narrowing of the brush receivingchannel until the at least one brush holder apparatus is held securelyby the at least one connector.

In accordance with still another aspect of the present invention, amethod includes the steps of: a) providing: a motor housing including:at least one brush receptacle extending along a longitudinal axis of thebrush receptacle and having a top end and a bottom end that aresubstantially parallel to the longitudinal axis; a locking elementextending from the top end toward the bottom end of each brushreceptacle; and a cantilevered housing spring member having a distal endextending substantially along the longitudinal axis and extending fromthe bottom end toward the top end of each brush receptacle; at least onebrush holder apparatus including: a brush holder housing sized to bereceived within the at least one brush receptacle, including: an uppersurface and a lower surface that are substantially parallel; a firstreceiving aperture in the upper surface configured to receive thelocking element when the brush holder housing is inserted inside the atleast one brush receptacle; and an open end that is substantiallyperpendicular to the upper surface; a brush spring enclosed by the brushholder housing; and a brush located inside the brush holder housing buturged out of the open end of the brush holder housing by the brushspring along the longitudinal axis when the brush holder housing isinserted inside the at least one brush receptacle; b) inserting the atleast one brush holder apparatus, the open end first, into the at leastone brush receptacle along the longitudinal axis, causing the housingspring member to move away from the top end of the brush receptacle; c)aligning the locking element with the first receiving aperture; and d)allowing the housing spring member to urge the brush holder apparatustoward the top end of the brush receptacle and causing the firstreceiving apparatus to receive the locking element.

Still other benefits and advantages of the invention will becomeapparent to those skilled in the art to which it pertains upon a readingand understanding of the following detailed specification.

III. BRIEF DESCRIPTION OF THE DRAWINGS

The invention may take physical form in certain parts and arrangement ofparts, embodiments of which will be described in detail in thisspecification and illustrated in the accompanying drawings which form apart hereof and wherein:

FIG. 1 is a perspective view of an assembled motor.

FIG. 2 is a perspective view of a disassembled motor.

FIG. 3 is a cross-sectional perspective view of a brush holder apparatusinstalled in a motor housing.

FIG. 4 is a perspective view of an insulation displacement connector.

FIG. 5 is a perspective view of an insulation displacement connectorinstalled in a terminal board.

FIG. 6 is a perspective view of an insulation displacement connectorcontacting a brush holder apparatus.

FIG. 7 is a view of a flat sheet cut out in the shape of an insulationdisplacement connector.

FIG. 8 is a bottom view of an insulation displacement connector.

FIG. 9 is an end view of a motor.

IV. DETAILED DESCRIPTION

Referring now to the drawings wherein the showings are for purposes ofillustrating embodiments of the invention only and not for purposes oflimiting the same, and wherein like reference numerals are understood torefer to like components, FIG. 1 shows an assembled electric motor 2.The motor 2 may have a motor housing 20 that receives and secures atleast one brush holder apparatus 10. In one embodiment, the motorhousing 20 may be made from electrically insulating materials; anon-limiting example of such a material would be plastic or polymer. Inanother embodiment, the housing 20 may be made from a conductivematerial. Motors 2 may include any DC, AC, or universal motors that usebrushes. Such motors may be used in applications that include, but arenot limited to, blenders, vacuum cleaners, air compressors, and otherdevices.

FIG. 2 shows a perspective view of a disassembled motor 2. The motor mayfurther include an armature 3, which has a commutator 4, and a field 5.The armature 3 may be inserted along a motor axis 26 (aligned with themotor shaft) inside the field 5 and both 3, 5 placed inside the motorhousing 20 such that at least a portion of the field 5 is housed insidethe housing 20, as shown in FIG. 1. If the motor housing 20 is made froma conductive material, insulation may isolate the housing 20 from thearmature 3, the field 5, and the brush holder apparatus 10.

With continued reference to FIG. 2, one embodiment of the motor 2 mayinclude two brush holder apparatuses 10. In another embodiment, the twobrush holder apparatuses 10 may be positioned within the motor housing20 opposite each other, aligned along a common axis 7. In anotherembodiment, the two brush holder apparatuses 10 may be offset from acommon axis 7 within the motor housing 20; FIG. 9 shows such an example.In another embodiment, the offset brush holder apparatuses 10 may beparallel to each other. In alternative embodiments, as many brush holderapparatuses 10 as needed may be used. In another embodiment, the brushholder apparatuses 10 may be positioned at corners of a substantiallyrectangular housing 20. The brush holder apparatus 10 may include abrush holder housing 9 and a brush 8. In one embodiment, the brush 8 maybe made from carbon. In one embodiment, the brush holder housing 9 maybe made from a conductive material, including, but not limited to,brass, copper, silver, gold, and aluminum. In alternative embodiments,the brush holder housing 9 may be made from a nonconductive material,including, but not limited to, polymer and rubber.

With continued reference to FIG. 2, the motor housing 20 may include atleast one brush receptacle 24 sized to receive the at least one brushholder apparatus 10. In alternative embodiments, the housing 20 mayinclude as many brush receptacles 24 as there are brush holderapparatuses 10. The brush holder apparatus 10 may be inserted into thebrush receptacle 24 from outside the housing 20 inwards along theapparatus's (or the brush receptacle's 24) longitudinal axis 7 andperpendicular to the motor axis 26. The armature 3 and field 5 may besecured inside the housing 20 such that the field 5 encircles andmatches the armature 3 and the brush holder apparatus 10, when installedinside the brush receptacle 24, is aligned such that the brush 8contacts the commutator 4.

FIG. 3 shows a partial cross-sectional view of a brush holder apparatus10 installed in a brush receptacle 24 of the motor housing 20. While itis known in the art to secure a brush holder to a motor housing, what isnot known is how to achieve a secure attachment by integrating thesecuring features into the housing 20 and the brush holder apparatus 10,thus eliminating fasteners, adhesives, and additional assembly steps. Abrush holder apparatus 10 may take the form of a substantiallyfour-sided brush holder housing 9 extended along a longitudinal axis 7of the brush holder apparatus 10. In alternative embodiments, the brushholder housing 9 may be a rectangular prism, or may have some roundedsides, as shown in FIG. 6. A brush spring 6 may be secured inside thebrush holder housing 9 to urge the brush 8 out of an open end of thebrush holder housing 9 such that the brush 8 may contact the commutator4 when the motor 2 is assembled. The brush holder apparatus 10 may havereceiving apertures 11 formed on its upper and lower surfaces. Thesereceiving apertures 11 may have locating elements 12 substantiallyadjacent to the location of the apertures 11. The locating elements 12may extend above the upper and lower surfaces of the brush holderapparatus 10 away from the lower and upper surfaces, respectively. Inanother embodiment, the brush holder apparatus 10 may have only onereceiving aperture 11 and locating element 12.

With continued reference to FIG. 3, extending down from the top interiorsurface or end of the brush receptacle 24 toward its bottom end may be alocking element 21. The description of a top or bottom end or surface isan arbitrary reference point, and such surfaces or ends may be orientedin any other direction or angle. The position, size, and shape of thelocking element 21 may be such that when the brush holder apparatus 10is put into the brush receptacle 24, the locking element 21 is receivedinside the receiving aperture 11. Formed into the brush receptacle 24and located adjacent to the locking element 21 may be a recessed pocket22. The recessed pocket 22 provides clearance for the locating element12 so that the brush holder apparatus 10 may be inserted into the brushreceptacle 24 without interference. A surface 25 common to the recessedpocket 22 and the locking element 21 may cooperate with the locatingelement 12 to locate the brush holder apparatus 10 along thelongitudinal axis 7.

With continued reference to FIG. 3, also contained within the brushreceptacle 24 may be a housing spring member 23 or spring. The housingspring member 23 may be located on an opposing surface or end of thebrush receptacle 24 from the locking element 21. The housing springmember 23 may be a substantially cantilevered element. Also, the housingspring member 23 may have its distal end angled upwards so that when thebush holder apparatus 10 is inserted into the brush receptacle 24, thebrush holder apparatus 10 forces the housing spring member 23 downwards.In this manner, the housing spring member 23 may apply an upward forceto the brush holder apparatus 10 and assist in retaining the lockingelement 21 in the receiving aperture 11. In one embodiment, the housingspring member 23 may also be made from electrically insulatingmaterials; a non-limiting example of such a material would be plastic.

FIG. 4 shows one embodiment of an insulation displacement connector(IDC) 30. FIG. 8 shows a bottom view of the same IDC 30. While it isknown in the art to electrically connect a brush holder to an electricmotor field, what is not known is how to achieve this connection byintegrating the securing features and connection features into theelectrical connection member and providing a robust electricalconnection, reduced components, and reduced assembly time. The IDC 30may be made from electrically conductive material; non-limiting examplesof such a material are brass, copper, silver, gold, and aluminum. In oneembodiment, an IDC 30 may be made from one, integral flat sheet orpattern using a metal forming process, as shown in FIG. 7.

With continued reference to FIG. 4, the IDC 30 may contain a pluralityof displacement members 31 or plates. Each displacement member 31 mayhave a cutting portion 33 at its distal end. The cutting portion 33 maybe shaped and sized to receive insulation coated electrical wire 50, asshown in FIG. 5. Also, the cutting portion 33 may be shaped and sizedsuch that when force is applied to the displacement member 31 with wire50 in place, the cutting portion 3 displaces the insulation from thewire 50 and an electrical connection is made between the wire 50 and thedisplacement member 31. The cutting portion 33 may also be shaped andsized such that the insulation may be displaced from the wire 50 withoutinducing significant damage to the wire 50. One non-limiting example ofthe shape of a cutting portion 33 is a V shape where the wire 50 wouldlie in the V. The cutting portion 33 may be smaller than the diameter ofthe insulation on the wire 50 and thus cut the insulation when forcedagainst the wire 50.

With continued reference to FIG. 4, displacement members 31 may belocated along and perpendicular to the longitudinal or connector axis 37of the IDC 30. When arranged in this manner, the top surfaces ofdisplacement members 31 form a brush receiving plane 35. Also, thedisplacement members 31 may lie substantially parallel to each otherwith their respective cutting portions 33 aligned on a common centerline.

With continued reference to FIG. 4, a plurality of connector springmembers 32 may be located to form opposing sides to the displacementmembers 31. The top portion of the spring members 32 may extend abovethe brush receiving plane 35. The cutting portion 33 of the displacementmembers 31 may extend below the bottom portion of the spring members 32.The top portion of the spring members 32 and the brush receiving plane35 may form a brush receiving channel 34. The brush receiving channel 34may be sized to grip the brush holder apparatus 10. In this manner, thebrush receiving channel 34 may be wider at its receiving end andnarrower at its distal end. This difference in channel width may allowthe brush holder apparatus 10 to be inserted easily into the receivingend of the channel 34, but the spring members 32 may grip and applycontact pressure to the brush holder apparatus 10 at the distal end.This contact pressure may make an electrical connection between thebrush holder apparatus 10 and the IDC 30 and secure the brush holderapparatus 10 in the receiving channel 34. The brush receiving channel 34may run parallel to the IDC longitudinal axis 37. In one embodiment, theconnector spring members 32 may have a cantilever-shaped portion 36 attheir distal ends to grip the brush holder apparatus 10 and provide anelectrical connection.

FIG. 5 shows a partial view of a field 5, which may include a laminatedstator 51 and field windings 52 (which may be made up of a plurality ofturns of magnet wire, but which are represented as object 52 in FIG. 5).The field 5 may have a terminal board 40 secured to the field 5. Theterminal board 40 may be made from electrically insulating materials; anon-limiting example of such a material would be plastic. The terminalboard 40 may contain a plurality of terminal blocks 41. In oneembodiment, the terminal blocks 41 are molded into the terminal board40. A terminal block 41 may contain a connector receptacle 42. In oneembodiment, the receptacle 42 is molded into the terminal block 41. Theconnector receptacle 42 may be sized to receive and fixedly retain anIDC 30. The connector receptacle 42 may have a wire receptacle 43 sizedto receive and securely retain an electrical wire 50, which may beconnected to the field windings 52. The wire 50 may be insulated in oneembodiment. The wire receptacle 43 may be molded into the connectorreceptacle 42. The connector receptacle 42 and the wire receptacle 43may be located within the terminal block 41 such that they cooperate toalign the cutting portions 33 of the IDC 30 with the electrical wire 50.

With reference to FIGS. 2 and 5, one embodiment may include two IDCs 30.In another embodiment, the two IDCs 30 may be positioned on the field 5opposite each other. In alternative embodiments, as many IDCs 30 asneeded may be used. In another embodiment, the IDCs 30 may be positionedat corners of a substantially rectangular field 5. In anotherembodiment, as many IDCs 30 may be used as there are brush holderapparatuses 10. In another embodiment, the IDCs 30 may be positioned onthe field 5 to be aligned with and correspond to the brush receptacles24 when the field 5 is installed inside the motor housing 20.

In one embodiment, a brush holder apparatus 10 may be fixedly mated withthe electric motor housing 20 and obtain electrical connection with theIDC 30 according to the following method. With reference to FIGS. 2 and5-6, the user may align insulated electrical wire 50 connected to thefield windings 52 with the wire receptacle 43 on the terminal block 41and insert the wire 50 into the receptacle 43. The user may align theIDC 30 with the connector receptacle 42 such that the cutting portion 33engages the electrical wire 50. The user may forcibly insert the IDC 30into the connector receptacle 42, thus fixedly attaching the twoelements 30, 42. Forcibly inserting the IDC 30 in the receptacle 42 mayresult in the insulation on the outside of the electrical wire 50 to beremoved or pierced by the cutting portion 33, and thus an electricalconnection may be made between the wire 50 and the IDC 30. The insertionmay also result in the IDC 30 being fixedly mated with the terminalboard 40. The user may repeat this procedure for every IDC 30. With theIDCs 30 secured to the field 5, the armature 3 may be inserted insidethe field 5, and both 3, 5 may be placed inside the motor housing 20, aspreviously described, such that the brush receiving channels 34 of theIDCs 30 align with the brush receptacles 24 of the housing 20.

Having assembled the field 5, the armature 3, and the housing 20, thebrush holder apparatuses 10 may be installed. As shown in FIGS. 1-3 and6, the user may next align the longitudinal axis 7 of the brush holderapparatus 10 with longitudinal axis of the brush receptacle 24 (and alsowith the connector axis 37 and channel 34 of the IDC 30). The user mayforcibly insert the brush holder apparatus 10 into the brush receptacle24 with the open end of the brush holder housing going in first. As thebrush holder apparatus 10 moves into the brush receptacle 24, the brushholder apparatus 10 may displace the housing spring member 23 downwardor away from the brush holder apparatus 10. In one embodiment, the brushholder apparatus 10 may be inserted in the brush receptacle 24 until thelocking element 21 aligns with the receiving aperture 11. In anotherembodiment, the brush holder apparatus 10 may be inserted in the brushreceptacle 24 until the locating element 12 rests against the surface 25of the locking element 21. The user may align one receiving aperture 11with one locking element 21 located inside the brush receptacle 24. Atthis point, the user may release the brush holder apparatus 10, whichwill allow the spring force of the spring member 23 to move the brushholder apparatus 10 in an upward direction, thus seating the lockingelement 21 into the receiving aperture 11. The locating element 12 andthe locking element 21 may cooperate to prevent the brush holder housing9 from being inserted too far and jamming the commutator 4. Thereceiving aperture 11 and the locking element 21 may cooperate toprevent the brush holder housing 9 from being pushed back out of themotor housing 20 by the spring force of the brush 8 against thecommutator 4.

In one embodiment, the brush holder apparatus 10 may have receivingapertures 11 and locking elements 12 on both its upper and lower sides,which may be mirror images, thus allowing two possible insertionorientations one hundred and eighty degrees apart. By having twopossible insertion orientations, it may become easier for the user toalign the brush holder apparatus 10 with the locking element 21 duringassembly; the user does not have to pay attention as to the specificorientation of the brush holder apparatus 10 during its insertion intothe brush receptacle 24 because either of the two insertions will work.

In another embodiment, the brush holder apparatuses 10 may be installedin the motor housing 20 offset from a common axis 7, as explainedpreviously and shown in FIG. 9. Such offset may allow more surface-areacontact between the brush 8 and the commutator 4 for the same size brush8, which may increase the life of the brush 8. In one embodiment ofoffset brush holder apparatuses 10, each brush holder apparatus 10 mayhave only one receiving aperture 11 and locking element 12, which mayallow only one insertion orientation and prevent improper assembly.

With reference to FIGS. 3 and 6, as the brush holder apparatus 10 isbeing inserted into the brush receptacle 24, it 10 may move into thebrush receiving channel 34 of the IDC 30. The connector spring members32 may apply contact pressure to the sides of the brush holder apparatus10, as shown in FIG. 6. This contact pressure may aid in retaining thebrush holder apparatus 10 in the motor housing 20 and may also providean electrical connection between the brush holder apparatus 10 and theIDC 30. FIG. 6 does not show the motor housing 20 that would enclose theIDC 30 and into which the brush holder apparatus 10 would be inserted.As shown partly in FIG. 3, the brush holder apparatus 10 may be retainedby the connector spring members 32 at the side that is urged by thehousing spring member 23 and opposite from the side that receives thelocking element 21 in the receiving aperture 11.

At this point, all of the components of the motor 2 may be secured suchthat the brush spring 6 urges the brush 8 to contact the commutator 4that is located inside the housing 20 and is aligned with the brushholder apparatus 10. Electricity may now be conducted from the fieldwindings 52 through the wire 50 inside the wire receptacle 43, throughthe IDC 30 that pierces the insulation of and makes electrical contactwith the wire 50, through the brush holder housing 9 that is securedinside the IDC channel 34, through the brush 8 that is housed inside thebrush holder housing 9, and to the commutator 4 that is contacted by thebrush 8. By this method, the brush holder apparatus 10 may be securedinside a motor 2 and may make electrical connection with the fieldwindings 52. In other embodiments, a motor 2 may include the meansdisclosed here to physically secure the brush holder apparatus 10 insidethe motor 2 (by virtue of the design of the brush holder apparatus 10and the motor housing 20) but use a different means for electricalconnection to the brush holder apparatus 10 (and not have the disclosedIDC 30). In other embodiments, a motor 2 may include the means disclosedhere for electrical connection to the brush holder apparatus 10 (by theIDC 30) but use a different means to physically secure the brush holderapparatus 10 inside the motor 2 (and not use the disclosed design of thebrush holder apparatus 10 and the motor housing 20).

Numerous embodiments have been described, hereinabove. It will beapparent to those skilled in the art that the above methods andapparatuses may incorporate changes and modifications without departingfrom the general scope of this invention. It is intended to include allsuch modifications and alterations in so far as they come within thescope of the appended claims or the equivalents thereof

Having thus described the invention, it is now claimed:

I/We claim:
 1. A motor assembly comprising: a motor housing comprising:at least one brush receptacle extending along a longitudinal axis of thebrush receptacle and having a top end and a bottom end that aresubstantially parallel to the longitudinal axis; a locking elementextending from the top end toward the bottom end of each brushreceptacle; and a cantilevered housing spring member having a distal endextending substantially along the longitudinal axis and extending fromthe bottom end toward the top end of each brush receptacle; and at leastone brush holder apparatus comprising: a brush holder housing sized tobe received within the at least one brush receptacle, comprising: anupper surface and a lower surface that are substantially parallel; afirst receiving aperture in the upper surface configured to receive thelocking element when the brush holder housing is inserted inside the atleast one brush receptacle; and an open end that is substantiallyperpendicular to the upper surface; a brush spring enclosed by the brushholder housing; and a brush located inside the brush holder housing buturged out of the open end of the brush holder housing by the brushspring along the longitudinal axis when the brush holder housing isinserted inside the at least one brush receptacle; wherein the at leastone brush holder apparatus is inserted inside the at least one brushreceptacle along the longitudinal axis; and wherein the housing springmember urges the at least one brush holder apparatus toward the top endof the at least one brush receptacle such that the locking element isreceived inside the first receiving aperture.
 2. A method comprising thesteps of: a) providing: a motor housing comprising: at least one brushreceptacle extending along a longitudinal axis of the brush receptacleand having a top end and a bottom end that are substantially parallel tothe longitudinal axis; a locking element extending from the top endtoward the bottom end of each brush receptacle; and a cantileveredhousing spring member having a distal end extending substantially alongthe longitudinal axis and extending from the bottom end toward the topend of each brush receptacle; and at least one brush holder apparatuscomprising: a brush holder housing sized to be received within the atleast one brush receptacle, comprising: an upper surface and a lowersurface that are substantially parallel; a first receiving aperture inthe upper surface configured to receive the locking element when thebrush holder housing is inserted inside the at least one brushreceptacle; and an open end that is substantially perpendicular to theupper surface; a brush spring enclosed by the brush holder housing; anda brush located inside the brush holder housing but urged out of theopen end of the brush holder housing by the brush spring along thelongitudinal axis when the brush holder housing is inserted inside theat least one brush receptacle; b) inserting the at least one brushholder apparatus, the open end first, into the at least one brushreceptacle along the longitudinal axis, causing the housing springmember to move away from the top end of the brush receptacle; c)aligning the locking element with the first receiving aperture; and d)allowing the housing spring member to urge the brush holder apparatustoward the top end of the brush receptacle and causing the firstreceiving apparatus to receive the locking element.